Flame retardant resin compositions are utilized in various fields, such as electric and electronic fields and building material fields, for ensuring the safety from fire. In these resin compositions, halogen compounds, such as chlorine compounds or bromine compounds, have generally been used as flame retardants. In view of the recent increasing concern about environmental problems in European and other countries, various investigations have been made about the use of phosphorus-containing flame retardants and other halogen-free flame retardants.
However, when phosphorus-containing flame retardants such as phosphate ester compounds, red phosphorus and the like are used for attaining flame retardancy, there have been problems such that odors may emanate in the extrusion or molding step and the mechanical characteristics and thermal characteristics may be adversely affected. Therefore, various materials have been tested in search of flame retardants capable of taking the place of halogen compounds and phosphorus compounds.
Silicone compounds are known as halogen-free, phosphorus-free flame retardants. Thus, Japanese Kokai Publication Sho-54-36365 discloses a resin composition comprising a non-silicone polymer rendered flame retardancy with a silsesquioxane mainly comprising T units, and Japanese Kokai Publication Hei-10-139964 discloses a resin composition comprising an aromatic ring-containing non-silicone resin rendered flame retardancy with a silicone resin having T and D units.
However, in the silsesquioxane resin disclosed in Japanese Kokai Publication Sho-54-36365, an expensive silsesquioxane resin is required to be added in a large amount for attaining flame retardancy, hence it is impractical. The silicone resin described in Japanese Kokai Publication Hei-10-139964 is effective for polycarbonates but has little effect in rendering other resins flame retardancy, hence cannot provide them with a sufficient level of flame retardancy.